Moffitt Nephrology Report 10/9: Hypernatremia, SIADH vs CSW

Take-home pearl: in hypernatremia, there is much less evidence about the safe/ideal rate of correction. Some use a similar rate to hyponatremia correction (i.e. 10mEq/L per 24hrs). However, most of the time with our patients with hypernatremia, it tends to be acute and can be corrected relatively quickly.

Additional learning:

Some of the highest glucoses you will see in DKA or HHS are in patients with CKD. If you have functional kidneys, it is hard for the glucose to get too high because at some point with hyperglycemia it just spills over into the urine and gets excreted, unless there is decreased GFR.

SIADH vs cerebral salt wasting. What’s the deal?!? We asked Chi to share his thoughts about SIADH vs cerebral salt wasting and he gave us a nuanced and interesting response. In SIADH, we often teach that it is a water retention problem cause by ADH and that they are euvolemic. However, in reality if you retain a lot of free water, you will become hypervolemic. Therefore there must be some natriuresis to maintain euvolemia in SIADH. Cerebral salt-wasting is a similar process with increased ADH, however the natriuresis is abnormally exaggerated and causes hypovolemia. The pendulum has swung back and forth over the years about whether cerebral salt-wasting is a distinct entity. Chi thinks that it is, but is quite rare. Pathophysiology is unclear but there are some theories out there.

Check out this article (PMID: 18216309) for a commentary on Cerebral Salt Wasting vs SIADH to learn more